stephane-genicot.github.io

Bowling

About this Kata

This short and simple Kata should be performed using Test Driven Development (TDD).

This description is based on that at Adventures in C#: The Bowling Game

Create a program, which, given a valid sequence of rolls for one line of American Ten-Pin Bowling, produces the total score for the game. Here are some things that the program will not do:

Problem Description

• We will not check for valid rolls.
• We will not check for correct number of rolls and frames.
• We will not provide scores for intermediate frames.
• Depending on the application, this might or might not be a valid way to define a complete story, but we do it here for purposes of keeping the kata light. I think you’ll see that improvements like those above would go in readily if they were needed for real.

We can briefly summarize the scoring for this form of bowling:

• Each game, or “line” of bowling, includes ten turns, or “frames” for the bowler.
• In each frame, the bowler gets up to two tries to knock down all the pins.
• If in two tries, he fails to knock them all down, his score for that frame is the total number of pins knocked down in his two tries.
• If in two tries he knocks them all down, this is called a “spare” and his score for the frame is ten plus the number of pins knocked down on his next throw (in his next turn).
• If on his first try in the frame he knocks down all the pins, this is called a “strike”. His turn is over, and his score for the frame is ten plus the simple total of the pins knocked down in his next two rolls.
• If he gets a spare or strike in the last (tenth) frame, the bowler gets to throw one or two more bonus balls, respectively. These bonus throws are taken as part of the same turn. If the bonus throws knock down all the pins, the process does not repeat: the bonus throws are only used to calculate the score of the final frame.
• The game score is the total of all frame scores.

More info on the rules at : http://www.topendsports.com/sport/tenpin/scoring.htm

Clues

What makes this game interesting to score is the lookahead in the scoring for strike and spare. At the time we throw a strike or spare, we cannot calculate the frame score: we have to wait one or two frames to find out what the bonus is.

Suggested Test Cases

(When scoring “X” indicates a strike, “/” indicates a spare, “-” indicates a miss)

• X X X X X X X X X X X X (12 rolls: 12 strikes) = 10 frames * 30 points = 300
• 9- 9- 9- 9- 9- 9- 9- 9- 9- 9- (20 rolls: 10 pairs of 9 and miss) = 10 frames * 9 points = 90
• 5/ 5/ 5/ 5/ 5/ 5/ 5/ 5/ 5/ 5/5 (21 rolls: 10 pairs of 5 and spare, with a final 5) = 10 frames * 15 points = 150

Comments from those who have mastered this Kata

Write some thoughts here about what you have learnt from this Kata. You don’t have to post all the code of your solution - I think the solution in itself is less interesting than the path you took to get there and what decisions you made. Just seeing the code won’t necessarily help me to reproduce it for myself. So in this section various people might go through the main parts of the problem and how they tackled them, what design ideas were discarded, and which order the test cases were implemented in.

• One interesting point to note is that without counting frames in any way (although I don’t think this was intended as a ‘hard’ requirement for the initial Kata completion), finding an elegant way to identify the end of the game/last “real” frame becomes difficult (ie: assuming there are final ‘bonus’ rolls included in a given test case). Update : After trying various things, including writing out a logic matrix for possible end-of-game combinations, I’m not sure it’s possible to detect whether a final ‘throw’ counts as bonus-only or as part of an actual frame, unless you’re counting frames. – RudyXDesjardins

Useful link

The complete description can be found here : Coding Dojo

Clean Code - TDD : click here

IMPORTANT: Implement the requirements focusing on writing the best code you can produce.